The present invention relates to semiconductor devices and, more particularly, to a semiconductor device capable of testing a high voltage even after packaging.
In general, in semiconductor devices using a high voltage, a high voltage is tested and measured on a wafer in which elements are formed. This is a method of determining whether a high voltage is abnormal by performing the test before packaging. The high voltage is generally measured using a probe. The high voltage is measured according to the flowchart illustrated in FIG. 1.
FIG. 1 is a flowchart illustrating a method of measuring a high voltage of a conventional semiconductor device. A general high voltage test includes a test mode setup step P11, a high voltage generator enable step P12, a high voltage measured bit enable step P13, a measuring pad measurement step P14, and a high voltage generator disable step P15.
In particular, a target semiconductor device is set to test mode at step P11. At this time, the semiconductor device is tested on a wafer before packaging. A test signal is enabled using the high voltage generator at step P12. A measured bit signal for a high voltage test is enabled at step P13. The measurement pad compares the high voltage measured bit and a reference signal level to measure the difference at step P14, which tests the high voltage. After the measurement, the high voltage generator is disabled at step P15, thus finishing the high voltage test.
The high voltage test is performed according to the flowchart illustrated in FIG. 1, and a measurement thereof may vary. Before the test is performed on the wafer level, the level of an internally generated high voltage is measured, and is then compared with the required target level. A trimming circuit compensates for the difference between the level of the internally generated high voltage and the target level in order to set the level of the internally generated high voltage to a target value.
A general high voltage test method includes a first method of directly connecting a measurement probing pin to a mini-pad within a chip, and measuring a high voltage using an oscilloscope, and a second method of connecting an equipment apparatus to a measurement pad (referred to as “VEXTPAD”) to read a high voltage. The first method is generally used for design analysis. The second method is used to read an initial value for a wafer trimming, and is used for mass production.
However, if measurement and trimming in a wafer state are completed and packaging is completed through a packaging process, the mini-pad within the chip, and the measurement pad VEXTPAD cannot be electrically connected to external pins. It makes it very difficult to measure the high voltage. Thus, in the case where the high voltage circuit must be tested since abnormalities may occur in the operation of the device after packaging, the packaging has to be peeled off and the measurement has to be performed again. Furthermore, if the high voltage is measured through the pad, numerous measurement errors may occur due to the introduction of noise between the oscilloscope and the probe.